Processing issues and their influence in the magnetoelectric performance of (K,Na)NbO3/CoFe2O4-based layered composites

Reference Presenter Authors
08-073 Washington Santa Rosa Rosa, W.S.(Federal University of São Carlos); Venet Zambrano, M.(Federal University of São Carlos); Algueró, M.(Instituto de Ciencia de Materiales de Madrid); Amorín, H.(Instituto de Ciencia de Materiales de Madrid); M'Peko, J.(University of São Paulo); Low temperature processing of environmentally-friendly (K,Na)NbO3- and CoFe2O4-based layered composites has been accomplished by hot pressing, and their electrical, piezoelectric and magnetoelectric properties have been characterized. High quality composite three-layer CoFe2O4/K0.5Na0.5NbO3/CoFe2O4 structures with defect-free interfaces have been obtained by hot pressing at only 1000 ºC, when highly reactive CoFe2O4 powders obtained by Pechini are used. Negligible chemical reactions at, and interdiffusion across interfaces take place during the low temperature processing, while alkali volatilization is also minimized. Dense, crack-free CoFe2-zGazO4/(K0.5Na0.5)1-xLixNb1-yTayO3/CoFe2-zGazO4 structures incorporating phases with enhanced piezoresponse have been also obtained, though in this case both piezoelectric and magnetoelectric coefficients steadily increase with the hot pressing temperature up to 1100 ºC. This is shown to be related with the presence of core-shell type microstructure within the piezoelectric layer characteristic of (K0.5Na0.5)1-xLixNb1-yTayO3, and that is stabilized by the low temperature processing. Procedures for further enhancement of the magnetoelectric response are proposed.
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